Optical seekers for use in guidance of spinning projectiles or spinning missiles (hereinafter, when the term “projectile” is used, it should be understood that it relates also to a “missile”, and vice versa, when the term “missile” is used, it should be understood that it relates also to a “projectile”) are known in the art. Such a seeker generally senses during the projectile flight light that is emitted or reflected from the target, and produces a signal, which is proportional to the deviation of the projectile direction from correct course toward the emitted light, i.e., the target. The correcting signal is then conveyed to a guiding or correcting unit within the projectile, which in turn performs the required course correction.
WO 98/31978 discloses a reticle for use in a guidance seeker for a spinning projectile. The projectile has a front opening, through which the light from the target can enter, and an essentially cylindrical hollow behind said opening in which the reticle and some additional optical elements are disposed. On the reticle, opaque lines are disposed in a specific manner. Light coming from the object and passes through the reticle is interrupted on its way to a light sensor by said lines due to the spinning of the projectile, therefore producing a modulated light signal which is relative to the deviation of the projectile direction from the route to the target. This modulated light, when sensed by a light sensor suitable for sensing light in the relevant wavelength, can be used for correcting the projectile route toward the target. The arrangement as suggested in WO 98/31978 is well suited for analog signal processing. This is particularly due to the form of the signals produced by the seeker of WO 98/31978, signals which are generally Pulse Width Modulated (PWM) signals. Other publications disclose reticles which produce AM signals that can be interpreted in a similar manner.
It is an object of the invention to provide a seeker for use in guiding a spinning projectile, which is very simple, compact in structure, and more suitable for digital signal processing.
It is still another object of the present invention to simplify the manner and circuitry needed for the processing of the output signals.
It is another object of the invention to provide a seeker for use in guiding a spinning projectile, which can be mounted on a projectile or missile having essentially any caliber.
It is still another object of the invention to provide a seeker for use in guiding a spinning projectile, in which the number of optical and electrical elements is reduced to a minimum.
It is still another object of the invention to provide a seeker for use in guiding a spinning projectile, which is simple to manufacture.
Other objects of the invention will become apparent as the description proceeds.